Method of making stereotype mats



Patented July 9, 1929.

v UNITED-STATES PATENT OFFICE.

ABLIE W. SGHORGEB, OF MADISON, WISCONSIN, ASSTGNOR TO 0. I. BURGESS LABORA- TORIES, INC., 01 MADISON, WISCONSIN, A CORPORATION OF DELAWARE.

METHOD OF MAKING STEREOTYPE MATS.

No Drawing. r

This invention relates to stereotype mats and is an improvement on the method described in Letters Patent No. 1,524,155, granted to me on January 27, 1925.

The rapidity with which modern newspapers are printed is due largely to use of the stereotype mat, also known as a matrix, or don As soon as a form containing the type ias been set up, a stereotype mat is superimposed, then covered with blankets or felts and passed through a rolling machine,

whereby the mat acquires a reverse impression of the type. The mat, after drying, is placed in acasting machine where it is held in the form of a cylinder. l olten stereotype metal is now pouredinto the machine whereby-a metal cylinder or semi-circle is obtained containing onits surface an exact duplicate of the type in the original fiat form. The stereotype plateis then placed in a cylinder press whereby. papers can be printed at high speed. Several casts can be made easily andrapidly from the same mat so that a number of presses can be placed in operation almost simultaneously.

' There are two types of stereotype mats in commercial use, the so-called wet mat and the dry mat. The wet unit, which is in most extensive use, consists of two or three sheets of thin blotting paper and two to four sheets of tissue paper held together by a paste made of starch, dextrin, gum arabic, etc. The

' tissue is used on the face to obtain a sharp,

smooth impression. The wet mat, after having been built up, must be stored in a wet condition. This is a serious objection. Furthermore, it must be dried on the type form as otherwise itwould warpand shrink greatly.

lid

Considerable labor and much skill, judgment and experience isrequired to produce a satisfactory wet mat. The rush of work in a newspaper press room cannot tolerate unreliability in the qualityot the mats supplied to the casting machine. Without suitable mats the printing cylinders cannot be made and without these the printing cannotpro ceed. In a modern newspa er ofice an interruption or even delay Incident to bad workmanship on the wet mats, or; unreliability in the starch with which they are made is a serious matter. They have to be made up shortly rior to the time fixed for their use and wit out adequate opportunit for testing, excepting by actual use.v at by the time defects in material and workmanship Application filed spin a; 1927. Serial m. 182,545.

develop, the harm hasbeen done to the printer and to all those ramifications of the newspaper art which are dependent on the timely issuance of the paper from the press.

The dry mat on the other hand, can be stored in the dry state in any quantity, but previous to use must be conditioned by eing placed in a humidor where it takes up from 10 to 30% of moisture. It is then rolled on the form, removed, placed in a cylindrical scorcher where most of the moisture is removed in one or two minutes. It is then ready for use in the casting machine. From the standpoint of initial cost, speed, and case of manipulation it is preferable to use a dry mat instead of a wet mat. In getting out a rush edition where every second ,counts, it is obvious that greater'speed can bejobtaincd with :1 dr mat.

The ob ection to the dry mat as now being manufactured is that it has a rougher surface than the wet mat and does not give satisfactory impressions with half-tone blocks with a fine screen, and in general, lacks sha rpness of definition; The dry mat does not have the plasticity of a wet met, so that fractures may be produced during molding on the type, .into which the molten stereotype metal will run. On removing the casting, the face;- of the mat will be torn so that the mat can .molten inetal will flow amid t 1e fibers, the

surface of the mat becoming torn when the casting is removechso that both the casting and the mat may be rendered useless.

It is not possible to obtain a satisfactory heat by the use of large quantities of ad hesives, such as are frequently employed, 0W7 ing to the fact that the mat when dry is not plastic, and if used wet it has all the disadvantages alreadypointed out. I

With my invention, as will be described below, these objections are overcome by the use of relatively fine, short, soft fibers, termed into a sheet to give an article havmg a highdegree of smoothness, strength and Impressionability. x

The natural cellulosic fibers available for manufacture of paper are so long and smooth lid one another or are ruptured. In either case- I that when a sheet formed from them is subrag stock, cotton linters, wood pulp and simiapparatus,

lar fibers, either alone or mixed, are placed in a paper-makers beater or other suitable and while suspended in water are subjected to a cutting and splitting action by suitably adjusting the beater roll with respect to the bed plate. After sufiic-ient beating, the original fibers will have been shortened in length and split longitudinally into small fibrils. The splitting action is complete in some fibers; in others the ends are separated into brushes and the'fibrils formed on the sides of the fiber given an arborescent appearance. The difference between the fibers before and after beating cannot well be shown in a pen and ink drawing, but is readily apparent under a microscope, particularly, if the fibers are stained in the well known manner. The relatively prolonged beating in water separates the fibers from one another by comblng out the pulp and without undue cutting or breakage of the whole fibers develops the fibrillated condition so important to the suc-.

cessful practice of the present invention. Other methods for fibrillating the fibers may be employed. When the fibers are combed out as described above and made into a sheet on the paper machine, the individual fibers are so interlocked out along the sides and ends of the individual by reason of the fibrils that stick v fibers'that the sheet as a whole acts somewhat like anet, permitting the required amount of stretching and plasticity during molding against the type, butwith adequate strength to permit the sheet subsequently tobe rolled into cylindrical form and with all the toughness and heat resistance needed for-a subsequent repeated contact with hot metal.

In Letters Patent 1,524,155, I follow the operation of beating the fibers by analkali cookmg operation to remove hydrated or gelatimzed cellulose which'may have formed durmg the beating operation. This gelatinized cellulose per se is objectionable since, when it dries, 1t hardens to a horn like brittle mass which shrinks enormously and has a prO- nounced tendency to warp and curl. The hydrated or gelatinized cellulose may be formed from the pure-cellulose fibers themselves after prolonged beating but it is much more readily formed from the various other carbohydrates and gelatini'zable materials. associated with cellulose fibers in nature. Chemical pulps from wood have a high percentage of such.

' the wood, well known to cotton linters.

readily gelatinizable materials present in the form of lignin, hemi-cellulose, hydro-cellulose, and oxycellulose. lulosic materials hydrolyze or gelatinize much more readily thanthe pure or alpha-cellulose. fibers when subjected to prolonged beating.

These forms of cel- The gelatinized cellulose is then easily dissolved or otherwise removed by cooking with an alkaline solution and separated from the purified fiber. The fibrillated fiber remaining is'used for making the dry stereotype mat. Wood per se is not used directly as the source of raw material for the beating operation but a chemical wood pulp, such as an easy-bleaching sulphite wood" pulp is ad\"antageously used. This preliminary chemical pulping of those skilled in the art, removes a large percentage of the easily gelatinizable impurities and breaks down the bundles of fibers of the wood so that the fibril lation operation may be more readily performed.

My'earlier the cellulosic gelatinized to an appreciable extent upon their exterior surfaces, removal of practically all of t e easily gelatinizable impurities, regardless of whether the raw stock was an impure chemical wood pulp or a purer form of cellulose fiber such as As a result of this excessive beating an alkaline cooking treatment was required in all cases after the beating operation to remove the gelatinized cellulose which causes the dried sheet to become hard, brittle, and have a low receptivity to impression. The fibrillated fibers obtained from the alkaline cook have excellent felting properties with no tendency to become hard or brittle on drying.

In my improved present specification, technique of the process of the manufacturer and invention contemplated beating method, the subject of the I have improved the from the standpoint have also found that the resulting'mat is superior to the mat made by my earlier process in those qualities nee-- fibers so that these fibers were thereb insuring the.

fied of easily gelatinizable materials prior to heating or otherwise treating the fiber to produce fibrillation, it is not necessary to follow the fibrillating operation by an alkaline cook. I have found thatsuflicient fibrillation may be secured with a minimum amount of gelatinization, whatever gelatinization occurring being insufiicient to affect the propertiesof the resulting mat adversely.

. If it is desirable to use cellulose fibers from wood because of their low cost. I have found that the impure fibers may be purified to yield a grade of fibre, high in alpha-cellulose,- WhlCh may be subJected to a beating operation without forming an undesirable amount ically alpha-cellulose.

of gelatinized cellulose incident with the desired degree of fibrillation. This pure cel-' stitutedltor the alpha-cellulose from wood.

. to cooking with alkali as made into using fibers so purified "that In the case of chemical wood pulps, I prefer they contain at lease 90 per cent alpha-cellulose and preferably 92 )e1' cent or more. i

ln preparing from wood a pulp high in alpha-cellulose excellent results are obtained- 3 using pulp prepared by the calcium-bisulpllite process, technically known as the sulphite process. Probably this process is especially suitable since it is effective in removing much of the helm-cellulose as Well as the other impurities from the wood during the cooking operation. The neutral sodium sulphite process is another chemical process which should yield a pulp suited to the making of fibers high in alpha-cellulose. If desired the sulphite or equivalent pulp may be subjectei'l to a bleaching operation previous this facilitates purification. After suitable washing, the pulp is subjected to cooking in an alkali solution to remove alarge proportion of the remaining impurities, especially those that are gelatinized readily. With an easy-bleaching sulphite wood-pulp, the alkali cooking solution may properly contain 10% of caustic soda based on the weight of the pulp, and the cooking maybe continued until the liquor is no longer alkaline to litmus. The heating or cooking may be performed at atmospheric pressure or at a steam pressure of 5 to 20 pounds. ,The amount of chemical used and the cooking conditions. employed will with the nature of the pulp. It will be understood, of course, that'other alkalis and a1- kaline earths may also be employed in the cooking liquor. The resulting fibers, after washing with water, are unchanged .in form, softeron drying, are high in alpha-cellulose and have a greatly reduced tendency to gelatinize on beatin The cooked ii are are thoroughly washed and are then subjected to the previously described heating or other fibrillating operation to secure suflicient fibrillation but without gelatinizing the fibers sufliciently to lower'the quality of the stereotype dry mat.

The fibrillated fibers are mixed with a suitable filler,

mats of the desired thickness, usually 0.030 inch. lt is preferable to build up a mat in several layers as this procedure gives greater uniformity and strength. Eight to ten layers have been found very satisfactory. This can be done by the use of various types of paper machines known to those skilled in the art.

The clay impregnates the entire sheet by vary such as a paper makers clay, and

'filling in the small interstices between the fibers, and the finished mat is strong,flexible and free from crevices. It-may be dried and.

stored like ordinary paper stock, and thequality of any batch maybe tested out long in advance of the time for usingthe batch 1n commercial press room work- To put the sheetsor mats in condition for v 7 any use it is only necessary to bring up their .moisture content in a humidor to that content best suited to the needs of the moment. A moisture content of 10 to 30%before scorching will be found suitable for most work.

A stereotype mat made as above described evcn'though classifiable as a dry mat and not a wet mat will give clear, pressions having smooth may be used for fine line reproductions with much the same results as a wet matan'd without any of the worrying uncertainties incident to wet mat production and use.

I claim: e

1. The method of making a stereotype dry mat which consists in fibrillating alpha-eel lulosc, mixing with a filler, and forming into sheets; substantially as described.

dense surfaces. It

deep and sharp im- 2. The method of making a stereotype dry mat which consists in fibrillating cellulosic fibers containing at least 90 per cent of alphacellulose and substantially free of readily gclatinizable substances, mixing with a filler and forming into sheets; substantially as described.

3. The method of making a stereotype dry gelatinizable materials from wood pulp, fibrillating said residual fibers,

mixing, with a filler and forming into sheets; substantially as described.

4. The method of making a stereotype dry mat whichconsists in removing substantially all of the readily wood pulp so that the residual fibers will contain at least 92 per cent of alpha-cellulose,

fibrillating said residual fibers, mixing with a filler and forming into sheets; substantially as described.

5. The method ofmaking a stereotype dry mat which consists in removing readily gelatinizable materials from chemical wood pulp by cooking said wood pulp in alkali, washing the dissolved materials from the residual fibers, fibrillating said residual fibers, mixing with a filler, and forn'iing' into sheets; substantially as described.

6. The method of making a stereotype dry mat which consists in cooking chemical wood pulp with alkali and removing the readily gelatinizable materials from the wood pulp so that the residual fibers will contain at least 90 percent of alpha-cellulose, fibrillating said residual fibers, mixing with clay and forming into sheets; substantially as described. 7. The method of making a stereotype dry mat which consists in cooking wood to a pulp gclatinizable materials from in a suitable chemical to dissolve a large part of the hemi-cellulose, washing said pulp with water, cooking, in alkali, washing with water, fibrillating' said pulp, mixing with a filler and forming into sheets -substantially as described.

8. The method of making a stereotype dry mat which consists in cooking sulphite wood pulp in alkali, washing with water, fibrillatiug said pulp, mixing with a filler and forming into sheex s; substantially as described.

9. The methodof making a stereotype dry mat which consists 1n cooking sulphlte wood pulp in mg said bleached pulp, mixing-with clay, forming into sheets composed of a plurality of like layers felted together and allowing said sheet to dry; substantially as described.

10. As a step in the manufacture of stereotype dry mats, the process which consists in cooking eellulosio'material in alkali to remove gelatinizable substances and then fibril-,

l lting, in part at iibers.

In testimony whereof I affix my signature.

ARLIE SCHORGER.

least, the residual cellulosic 

